Aventra converter fault

[trt]

It's being reported in the press that the Alstom Aventra trains being used on the LO, EL and elsewhere have a fault which has led to a memo being issued to Alstom staff in depots to avoid walking close by the electrical converter boxes on these units. The danger is reported as being an explosion risk caused by gas build up.

I'm wondering how much truth there is in these reports.

[Dstock7080]

Incident 19 May Plumstead sidings:

Background:
After a significant failure on Train 345003 at Plumstead sidings it has become apparent there is a potential risk to maintenance staff. Train 345003 suffered a failure of a capacitor in the traction system; this failure caused a significant over pressure event in the Convertor case which has caused a 7kg cover to become detached from the train.
This means there is a risk of serious injury or death when adjacent to the traction converter cases along the sides of the train
As such to protect maintenance staff NO ONE is allowed to work within 2 metres of the outside covers on the converter cases with power applied to the train. It is, however, permissible to walk past the converter if alternative options are not available as noted below
This brief is to be adopted for ALL AVENTRA fleets until further notice.
Instruction:
NO ONE is allowed to work within 2 metres of the outside covers on the converter cases with power applied to the train (i.e., Safety Conditions 2, 3 & 4).
2.
If practicable trains should be shutdown as much as possible when stabled
3.
If there is a choice of routes a route not passing a traction converter should always be used.
if personnel are situated on a platform road working on the train, at, or above, the height a station platform would be, then there is no restriction, this does not apply if the platform is staging.
5.
Walking past a converter is permissible if no other option is available, however make sure you are:
As far away from the converter as possible
b. Do not loiter by the converter
Walk as quickly, but safely, past as possible, taking no longer than 4 seconds to pass the converter.

[johnlinford]

Sounds similar to an explosion at Guildford a few years back on (I think) a class 450 - this link should be the RIAB report.

[Chris M]

Jun 8, 2022 19:10:44 GMT johnlinford said:

Sounds similar to an explosion at Guildford a few years back on (I think) a class 450 - this link should be the RIAB report.

It was a 455, but an explosion caused by the failure of a capacitor in a confined space is the same immediate cause.

[brigham]

"a significant over pressure event..."

What is the matter with these people? Do they talk like that in real life?

"Krakatoa was devastated by a significant over pressure event...

[trt]

Reading the RAIB report is interesting. Capacitor failures have been going on for years, including on the Northern Line. They came up with a method of detecting over pressure in capacitors (the event is caused by manufacturing defects rather than out of spec electric characteristics in the associated circuitry which IS controlled for) but the various manufacturers of the electrical control gear don't appear to employ this safety feature by default. New train models and controllers keep coming out with just over current / over voltage protection.
Thank you for the link to the report.

[jetblast787]

Surely these converters should have pressure relief valves as standard?

[d7666]

Jun 9, 2022 9:45:12 GMT jetblast787 said:

Surely these converters should have pressure relief valves as standard?

the part that is failing is a capacitor within the traction convertors - a pressure relief valve would be too late the thing has already seriously degraded if not exploded by the time a relief valve operated - what is needed is the above mentioned pressure detection before degradation progresses too far

[d7666]

Jun 9, 2022 7:42:27 GMT brigham said:

"a significant over pressure event..."

What is the matter with these people? Do they talk like that in real life?

"Krakatoa was devastated by a significant over pressure event...

Don't over pressure yourself thinking about that

[100andthirty]

I heard someone recently refer to a train failure as a significant thermal event. I said "do you mean in caught fire?" The response was "yes".

[trt]

And never forgetting 28th January 1986: "Obviously a major malfunction... [...] report from the flight dynamics officer that the vehicle has exploded."